Electron sources are employed for different applications such as X-ray systems like tomography (CT) and cardiovascular (CV) systems. These electron sources usually comprise thermionic emitters which emit electrons upon reaching a certain temperature. The filaments forming these thermionic emitters are necessarily made of metal with a high melting point, like tungsten, lanthanum or their alloys. These thermionic emitters are usually fixed to a cathode cup which primarily acts as an electron-optical focusing element.